In a wireless transmission process, a multipath effect and the like may cause fading on a transmitted signal, and especially, for a broadband system, in order to demodulate the fading signal, a channel state needs to be estimated, and the channel state is crucial for both a sender and a receiver. For example, a transmitter knowing a channel state may implement an optimal emission design, and a receiver may perform a balancing operation on a received signal according to the channel state, thereby implementing accurate demodulation on the received signal. Generally, a parameter related to the channel state may be calculated according to the received signal.